粤港澳闪电定位系统对高建筑物雷电的探测

Detection Results of Guangdong-Hongkong-Macao Lightning Location System for Tall-object Lightning

基于2016—2017年广州高建筑物雷电观测站获取的资料对粤港澳闪电定位系统(简称定位系统)的性能进行评估,并根据2014—2018年定位系统历史资料对广州高建筑物区域的雷电活动特征进行初步分析,结果表明:定位系统对闪电的探测效率为93%(214/229),对回击的探测效率为93%(449/481),对下行闪电首次回击、继后回击及上行闪电回击的定位误差的平均值(中值)分别为361 m(188 m)、252 m(167 m)和294 m(173 m);当接地点高度低于200 m(不低于200 m)时,定位系统对下行负极性闪电首次和继后回击的云闪/地闪识别正确率分别为99%(80%)和93%(35%),有83%的上行负地闪回击被定位系统误判为云闪,广州高建筑物区域内绝大部分负云闪定位记录实际是高建筑物地闪;对定位系统得到的孤立高建筑物闪电密度中心进行分析后发现,广州塔(600 m)闪电密度中心200 m半径范围内年均回击次数约为中信广场(390 m)和广发证券大厦(308 m)的5倍,推测广州塔闪电的主要类型为上行闪电,而中信广场和广发证券大厦则为下行闪电.

Tall-object lightning is one hot topic in the field of atmospheric electricity.In order to explore the application of Guangdong-Hong Kong-Macao Lightning Location System(GHMLLS)data on tall-object lightning,the performance of GHMLLS is evaluated based on the observation obtained at the Tall-Object Lightning Observatory in Guangzhou(TOLOG)during 2016 to 2017,and a preliminary comparative analysis on characteristics of lightning activities in the tall-object area in Guangzhou are made.Results show that the flash detection and the stroke detection of GHMLLS is about 93%(214/229)and 93%(449/481).The arithmetic mean(median)value of the location error is about 361 m(188 m),252 m(167 m)and 294 m(173 m)for downward first negative strokes,downward subsequent negative strokes and upward negative strokes respectively.It is found that the cloud-to-ground(CG)lightning with higher grounding points are more likely to be misidentified as intro-cloud(IC)lightning by the GHMLLS.When the grounding point is(is not)lower than 200 m,the identification accuracy of the IC/CG classification is 99%(80%)and 93%(35%),respectively,for downward first negative strokes and the subsequent negative strokes.The accuracy of the IC/CG classification for upward negative strokes is found to be only 17%.According to statistical results of GHMLLS dataset from 2014 to 2018,negative IC records in tall-object area in Guangzhou are found to be more prominently gathered near buildings with height over 300 m than CG records,indicating that most negative IC records are actually tall-object strokes but just misjudged by GHMLLS.Mean shift algorithm is used to identify the lightning density centers of three relatively isolated tall buildings,namely the Canton Tower(600 m),the CITIC Plaza(390 m)and the GF Securities Headquarters(308 m).It's found that the number of strokes within the radius of 200 m in the lightning density center of the Canton Tower is about 5 times as much as that of the CITIC Plaza or the GF Securities Headquarters.It is speculated that most lightning occurred on the Canton Tower belonging to upward type,while those hitting the CITIC Plaza and the GF Securities Headquarters are mainly downward type.